The circuit enables the determination of the temperature and the type of a battery i.e. the capacity of a battery. The information on the temperature and the capacity of a battery is required for the charging algorithm of an electrical apparatus such as a portable radio telephone with which the battery is to be used to ensure efficient and safe charging of the battery.
In a prior art circuit the temperature and battery type are measured from two distinct voltages, that is from measuring the voltage drop across two distinct resistance means. For this, two different physical connections between the battery and the electrical apparatus such as a portable radio telephone and two channels from the A/D converter of the electrical apparatus are required.
The prior art is described with reference to the accompanying drawings, in which:
FIG. 1 is a diagram of a prior art battery circuit; and
FIG. 2 is a diagram of a temperature curve indicative of the circuit described in FIG. 1.
The diagram shown in FIG. 1 is a circuit diagram of a prior art circuit. The temperature of the battery 1 is detected by measuring the voltage over the Negative Temperature Coefficient (NTC) resistor 2 in the battery 1 with the aid of the Analog to Digital (A/D) converter. The type of the battery 1 is determined likewise by measuring the voltage over the resistor 3 in the battery 1 with the aid of the A/D converter. The resistors used in the measurement have been marked with the numbers 4 and 5.
The diagram shown in FIG. 2 is a diagram of a temperature detection curve corresponding to the circuit described in FIG. 1. The relationship between the temperature of the battery 1 and the voltage measured over the NTC resistor 2 is described by tile curve 6. In addition, the value of the resistor 3 is selected depending on the type of the battery 1. Generally there are two to three different types of battery.
In the prior art circuit two different physical connections between the battery and the portable radio telephone and two channels from the A/D converter of the potable radio telephone are required.